Reduction by N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), a calmodulin antagonist, in the number of phorbol ester receptors in mouse skin.

A calmodulin antagonist, N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide (W-7), reduced the number of phorbol ester receptors in mouse skin in a dose- and time-dependent manner. The reduction occurred immediately after topical application of 30 mumoles of W-7, reaching a maximum of 86% after 5 min. Reduction in specific binding of 12-O-tetra-decanoylphorbol-13-acetate can explain the antitumor promoting activity of W-7 in mouse skin.